This invention relates to ceramic articles and has particular reference to a novel method of manufacturing such articles which permits them to be made on a mass-production basis at low cost.
Various methods for fabricating different kinds of articles using glass-forming materials, pulverized glass or quartz are known in the prior art. In U.S. Pat. No. 845,552 issued Feb. 26, 1907 to Jonkergouw, for example, there is disclosed a process for making glass articles by mixing glass-forming materials such as sand and carbonate of soda with borax and chalk, firing the mixture to produce a frit, and placing the latter into a mold and reheating it for 2 hours or so to form a fused body of glass having the desired shape. A method for forming a porous separator for a storage battery by placing glass particles in a mold and heating them to a temperature sufficient to frit or bond the particles together is disclosed in U.S. Pat. No. 1,051,638 issued Jan. 28, 1913 to Hugh Rodman. Other methods for forming articles by molding and firing a mixture of fused quartz particles and an inorganic binder, or a mixture of a binder such as wax and two powdered glasses that have different melting points, are described in U.S. Pat. Nos. 1,610,182 to Elihu Thompson and 2,197,562 to Gerald E. Reinker, respectively.
The prior art methods and compositions were unsatisfactory in that they required high-firing temperatures or long firing times, expensive raw-mix materials, and special molds or time-consuming operations which prevented the articles from being effectively mass produced.
Briefly, the present invention provides a composition and process which permit dense ceramic articles to be made on a mass production basis with inexpensive and readily available materials. These advantages are achieved by utilizing glass cullet, or other suitable scrap glass such as discarded bottles, as one of the basic ingredients of the raw-mix formulation. The scrap glass is pulverized and mixed with selected amounts of ball clay and a selected refractory mineral (preferably wollastonite) and molded into a compact at a pressure which permits the compact to be rapidly fired in air and transformed into a hard ceramic body of the desired configuration and dimensional tolerances. Selected amounts of bentonite and an inorganic pigment can also be included in the raw mix to facilitate the molding and firing operations and to give the finished article a pleasing body color.